To understand why it is **mandatory** to use the **rear fog lights** simultaneously with the **position lights**, it is important to know how and when these lights should be used.

- **Rear fog lights**: These lights are used in situations of **poor visibility**, such as dense fog, heavy rain, or snowfall. Their function is to make the vehicle more visible to drivers behind. They can be switched on together with other types of lights, such as the main and dipped beam lights, and the front fog lights.

- **Position lights**: These lights are essential for the vehicle to be visible in conditions of **low illumination**, such as when driving at night, in tunnels, or on dark days. When the vehicle is in motion, the position lights must always be on together with another type of lights.

Since the position lights must be on whenever the vehicle is moving and visibility conditions are poor, it is **mandatory** that they be used together with the rear fog lights to ensure maximum visibility and safety on the road.